Postgresql – insert is not working as expected while doing partitioning

Created a table with one column and sample values

create table t1 ();
alter table t1 add column id_ numeric;
insert into t1 values (generate_series(1,10));

And, done partitioning odd numbers in one table and even numbers in one table.

create table t1_odd (check (id_%2!=0)) inherits (t1);
create table t1_even (check (id_%2=0)) inherits (t1);

create table t1_r15 (check (id_<6)) inherits (t1);
create table t1_r510 (check (id_>4)) inherits (t1);

Call this function while insert or update anything in table t1

create or replace function t1_func() returns trigger as $$
begin
    if NEW.id_ % 2 != 0 then
       insert into t1_odd values (NEW.*);
    else
       insert into t1_even values (NEW.*);
    end if;
    return null;
end;
$$
language plpgsql;

create trigger t1_trig before insert or update on t1 for each row execute procedure t1_func();

Call this function while delete anything from table t1

create or replace function t1_rfunc() returns trigger as $$
begin
    if NEW.id_ < 5 then
        insert into t1_r15 values (NEW.*);
    else
        insert into t1_r510 values (NEW.*);
    end if;
    return null;
end;
$$
language plpgsql;

create trigger t1_rtrig before delete on t1 for each row execute procedure t1_rfunc();

It works fine for insert, and If i tried to update, getting some error

update t1 set id_ = id_ + 1;

gives

ERROR: new row for relation "t1_odd" violates check constraint "t1_odd_id__check"
SQL state: 23514
Detail: Failing row contains (2).

and while doing delete nothing gets inserted into t1_r15 or t1_r510 (data got removed from t1).

Am I missing anything?

(Using Postgresql 9.5)